Trustworthy timestamps and certifiable clocks using logs linked by cryptographic hashes

Abstract

A method and apparatus for creating and/or using trustworthy timestamps and certifiable clocks using logs linked by cryptographic hashes. In one embodiment, the method comprises maintaining a first, chained-hash log; associating a first clock with the chained-hash log, and entangling the first log; with a second by adding a time-stamped synchronization entry to the chained-hash log, where the synchronization entry has a second time indication associated with the second log and a hash of one or more entries in the first log.

We claim: 
     
       1. A method, comprising:
 maintaining, by a device that logs event times and document hashes, a first event log that is associated with a first clock; 
 entangling the first event log with a second event log maintained by another device; 
 tracing the entangling of the first event log with the second event log; and 
 annotating an entry in the first event log with a correction to a previously-issued timestamp in the entry based on results of tracing the entanglement, wherein an annotation of the entry in the first log is a new log entry in the first log that comprises a hash and a timestamp of the entry being annotated. 
 
     
     
       2. The method of  claim 1 , wherein the annotated entry is added to the first log as a connotation to a corrected entry in the first event log and indicates the corrected entry's error and a corresponding correction. 
     
     
       3. The method of  claim 1 , wherein entangling the first event log with a second event log and tracing the entangling further comprises:
 adding a time-stamped synchronization entry to the first log, the time-stamped synchronization entry having a time indication from a second clock of the another device that is associated with the second event log; and 
 tracing the entangling of the first event log back to the second clock, wherein the second clock is trustworthy. 
 
     
     
       4. The method of  claim 1 , further comprising:
 adding a time-stamped log entry from the first event log into the second event log, the time-stamped log entry containing a second time-stamped synchronization entry and a hash of the first event log. 
 
     
     
       5. The method of  claim 1 , further comprising:
 determining a level of accuracy of the second clock based on an assessment of accuracy of the trustworthy clock; and 
 determining reliability of timestamps in time-stamped log entries in the first event log based on observed accuracy of the trustworthy clock and a reputation of the another device that maintains the trustworthy clock. 
 
     
     
       6. The method of  claim 5 , wherein the another device is a network time protocol (NTP) server. 
     
     
       7. The method of  claim 5 , wherein the another device is a global positioning system (GPS) device. 
     
     
       8. The method of  claim 1 , wherein the second clock that is trustworthy has a known relationship to a trusted time standard. 
     
     
       9. A non-transitory computer readable storage medium including instructions that, when executed by a processor, cause the processor to perform a method comprising:
 maintaining, by a device that logs event times and document hashes, a first event log that is associated with a first clock; 
 entangling the first event log with a second event log maintained by another device; 
 tracing the entangling of the first event log with the second event log; and 
 annotating an entry in the first event log with a correction to a previously-issued timestamp in the entry based on results of tracing the entanglement, wherein an annotation of the entry in the first log is a new log entry in the first log that comprises a hash and a timestamp of the entry being annotated. 
 
     
     
       10. The non-transitory computer readable storage medium of  claim 9 , wherein the annotated entry is added to the first log as a connotation to a corrected entry in the first event log and indicates the corrected entry's error and a corresponding correction. 
     
     
       11. The non-transitory computer readable storage medium of  claim 9 , wherein entangling the first event log with a second event log and tracing the entangling further comprises:
 adding a time-stamped synchronization entry to the first log, the time-stamped synchronization entry having a time indication from a second clock of the another device that is associated with the second event log; and 
 tracing the entangling of the first event log back to the second clock, wherein the second clock is trustworthy. 
 
     
     
       12. The non-transitory computer readable storage medium of  claim 9 , further comprising:
 adding a time-stamped log entry from the first event log into the second event log, the time-stamped log entry containing a second time-stamped synchronization entry and a hash of the first event log. 
 
     
     
       13. The non-transitory computer readable storage medium of  claim 9 , further comprising:
 determining a level of accuracy of the second clock based on an assessment of accuracy of the trustworthy clock; and 
 determining reliability of timestamps in time-stamped log entries in the first event log based on observed accuracy of the trustworthy clock and a reputation of the another device that maintains the trustworthy clock. 
 
     
     
       14. The non-transitory computer readable storage medium of  claim 13 , wherein the another device is a network time protocol (NTP) server. 
     
     
       15. The non-transitory computer readable storage medium of  claim 13 , wherein the another device is a global positioning system (GPS) device. 
     
     
       16. The non-transitory computer readable storage medium of  claim 9 , wherein the second clock that is trustworthy has a known relationship to a trusted time standard. 
     
     
       17. A system comprising:
 a memory to store a first event log with log entries that comprise event times and document hashes; and 
 a processor to
 maintain the first event log that is associated with a first clock, 
 entangle the first event log with a second event log maintained by another device, 
 trace the entangling of the first event log with the second event log, and 
 annotate an entry in the first event log with a correction to a previously-issued timestamp in the entry based on results of tracing the entanglement, wherein an annotation of the entry in the first log is a new log entry in the first log that comprises a hash and a timestamp of the entry being annotated.